Biomedical subjects

M C Willingham

Publications and source records attributed to M C Willingham.

At least 91 records · Page 5Linked to original sources

PubMed1993

A human mitochondrial ATP-dependent protease that is highly homologous to bacterial Lon protease.

We have cloned a human ATP-dependent protease that is highly homologous to members of the bacterial Lon protease family. The cloned gene encodes a protein of 963 amino acids with a calculated molecular mass of 106 kDa, slightly higher than that observed by Western blotting the protein from human tissues and cell lines (100 kDa). A single species of mRNA was found for this Lon protease in all human tissues examined. The protease is encoded in the nucleus, and the amino-terminal portion of the protein sequence contains a potential mitochondrial targeting presequence. Immunofluorescence microscopy suggested a predominantly mitochondrial localization for the Lon protease in cultured human cells. A truncated LON gene, in which translation was initiated at Met118 of the coding sequence, was expressed in Escherichia coli and produced a protease that degraded alpha-casein in vitro in an ATP-dependent manner and had other properties similar to E. coli Lon protease.

ATP-Dependent Proteases↗

PubMed1993

PR1--a monoclonal antibody that reacts with an antigen on the surface of normal and malignant prostate cells.

BACKGROUND: The principal treatment for prostate cancer is surgery; prostate cancer is resistant to the common anticancer drugs. The only useful therapy for metastases involves diminishing testosterone levels by orchiectomy or administration of drugs, either of which may increase survival time. One approach to prostate cancer treatment is to use a monoclonal antibody (MAb) to target cytotoxic substances to these cancer cells. The MAbs available either do not react uniformly with prostate cancer cells or react with normal tissues. Thus, a new MAb is needed. PURPOSE: The goal of this study was to isolate an MAb that reacts with an antigen present on the surface of prostate cancer cells. METHODS: A strain of prostate cancer cells was isolated from a prostate cancer specimen, grown for 2-4 weeks in short-term culture, and used to immunize BALB/c mice. Hybridomas were then prepared by using spleen cells from the immunized mice. One hybridoma produced an MAb (PR1) that reacted with prostate cancers. RESULTS: MAb PR1 is an IgMK subtype that reacts uniformly with the surface of most (25 of 26) adenocarcinomas of the prostate. It also reacts with the surface antigen on normal prostate epithelial cells and on cells from benign prostatic hyperplasia. MAb PR1 reacts with a limited number of normal tissues including a subset of principal cells located in the collecting ducts of the kidney. CONCLUSION: We conclude that MAb PR1 reacts with a differentiation antigen present in normal prostate and that this antigen continues to be expressed on almost all adenocarcinomas of the prostate. IMPLICATIONS: This antibody may be useful for the diagnosis of or therapy for prostate cancer.

Adenocarcinoma↗

PubMed1993

Ultrastructural localization of daunomycin in multidrug-resistant cultured cells with modulation of the multidrug transporter.

We localized the chemotherapeutic drug daunomycin inside cultured cells by taking advantage of its inherent fluorescence. Multidrug-resistant cultured cells, in which the accumulation of daunomycin can be reversibly controlled with verapamil to block the multidrug transporter, were incubated in daunomycin and verapamil and the accumulated daunomycin was visualized with epifluorescence optics. After fixation under a variety of different conditions to make cells permeable to diaminobenzidine (DAB), the internal daunomycin was illuminated under the fluorescence microscope in the presence of DAB. Photooxidation of DAB in sites of fluorescing daunomycin (photoconversion) resulted in intracellular deposition of oxidized DAB product. These sites were then visualized by transmission electron microscopy. In cells in which the multidrug transporter was inhibited by verapamil, daunomycin was localized in the nucleus of cells by mild fixation conditions such as formaldehyde. Increasing amounts of glutaraldehyde in the fixative caused apparent quenching of the nuclear fluorescence but still allowed fluorescence to occur in other cell organelles, which were then well preserved. Daunomycin was found in the nuclear envelope, the endoplasmic reticulum, and in lysosomes in cells in which the multidrug transporter was inhibited. Lysosomal accumulation has been previously described and was expected because of the known accumulation of positively charged molecules in organelles with low pH. However, the accumulation of daunomycin in the nuclear envelope and endoplasmic reticulum has not been previously observed. These results clearly demonstrate the utility of fluorescence photoconversion methodology for the high-resolution ultrastructural localization of fluorescent materials.

3T3 Cells↗

PubMed1992

Identification of residues in the first cytoplasmic loop of P-glycoprotein involved in the function of chimeric human MDR1-MDR2 transporters.

The human MDR1 gene encodes the multidrug transporter (P-glycoprotein), a multidrug efflux pump. The highly homologous MDR2 gene product does not appear to be a functional multidrug pump. We have constructed a chimeric protein in which the first intracytoplasmic loop and the third and fourth transmembrane domains of the MDR1 protein were replaced by the analogous region of MDR2. Substitution of the MDR2 sequences encompassing amino acid residues 140 to 229 resulted in 17 amino acid changes, 10 in the intracytoplasmic loop (amino acids 141-188) and 7 in the transmembrane regions. This chimeric protein was expressed on the surface of NIH 3T3 cells where it bound [3H]azidopine but did not confer drug resistance. When only 4 residues, 165, 166, 168, and 169, were changed back to MDR1 amino acids, a functional drug transporter was recovered. When residues 165, 166, 168, and 169 from MDR2 were substituted into a functional MDR1 cDNA, the resulting construction was not able to confer drug resistance. These results indicate that the major functional differences between MDR1 and MDR2 in this region of P-glycoprotein reside in a small segment of the first intracytoplasmic loop. We also independently analyzed the effect of replacing Asn183 of MDR1 with Ser which occurs in MDR2. Substitution of Ser at position 183 in combination with Val at position 185 in P-glycoprotein resulted in a relative increase in resistance to actinomycin D, vinblastine, and doxorubicin in transfected NIH 3T3 cells. These results emphasize the importance of the first intracytoplasmic loop in P-glycoprotein in determining function and relative drug specificity of the transporter.

3T3 Cells↗

PubMed1992

Frequent expression of the tumor antigen CAK1 in squamous-cell carcinomas.

K1 is a murine monoclonal antibody (MAb) derived from a hybridoma generated by the fusion of splenocytes of BALB/c mice immunized with a human ovarian tumor cell line, OVCAR-3. This antibody reacts strongly with epithelial ovarian tumors and mesotheliomas. The antigen recognized by MAb K1, designated CAK1, has recently been characterized as a 40-kDa protein probably anchored to the cell surface by glycosyl-phosphatidylinositol. Using immunoperoxidase histochemical methods, we examined 37 squamous-cell carcinoma (SqCC) samples from cervix, lung, esophagus and other origins, and 12 normal squamous epithelia of the cervix and esophagus for their reactivity with MAb K1. Of the SqCC specimens, 81% showed K1 reactivity with variable intensity, but none of 12 normal tissue samples of squamous epithelia did so. Two patterns of CAK1 expression in tumor samples were found, i.e., a heterogeneous pattern with strong intensity, and a homogeneous pattern with weak intensity. Three carcinomas in situ of the larynx, vulva and esophagus were moderately positive with K1, suggesting that CAK1 antigen may occur in the early stage of carcinogenesis of SqCC. The expression of CAK1 was also compared with expression of CA125, HER-2/neu, p53 and P-glycoprotein, and MAb K1 was found to react most consistently with SqCC. Since K1 reacts with a majority of cervical and esophageal carcinomas but has no detectable reactivity in normal epithelia of the cervix uteri and esophagus, MAb K1 could be of value as a reagent to help distinguish between normal and neoplastic cells on sections as well as in cytological samples.

1-Butanol↗

PubMed1992

Antitumor effects of B3-PE and B3-LysPE40 in a nude mouse model of human breast cancer and the evaluation of B3-PE toxicity in monkeys.

B3 is a tumor-reactive monoclonal antibody (mAb) that binds to a limited number of normal tissues. Immunotoxins made with B3 coupled to either Pseudomonas exotoxin (PE) or recombinant forms of PE with a deletion of the cell-binding domain (LysPE40) have been shown to cause complete tumor regression in nude mice bearing a rapidly growing A431 (L. H. Pai et al., Proc. Natl. Acad. Sci. USA, 88: 3358-3362, 1991) human epidermoid carcinoma. In this study we show that an immunotoxin composed of mAb B3 when chemically coupled to LysPE40 (B3-LysPE40) led to complete regression of a slowly growing breast cancer, MCF-7, in nude mice when given i.v. every other day for five doses. mAb B3 coupled to native PE also produced significant regression of the MCF-7 tumor. The reactivity of mAb B3 was evaluated using an immunohistochemical method on the two responsive tumors, MCF-7 and A431, and compared with a typical human colon carcinoma specimen that has B3 antigen on its surface. The results showed that both A431 and MCF-7 xenograft tumors have similar reactivity to B3 when compared with the human colon carcinoma specimen. To evaluate the toxicity of B3-PE in primates, Cynomolgus monkeys received escalating doses of B3-PE i.v. on Days 1, 3, and 5. Based on antibody localization studies using frozen sections of normal human and monkey tissue, gastric, trachea, and bladder mucosal injury could have occurred. However, no clinical signs of injury or histological damage to these organs were seen at the doses administered. Chemical hepatitis due to PE was transient and well tolerated at doses up to 50 micrograms/kg for three doses. The lethal dose was about 100 micrograms/kg, and the cause of death was liver necrosis, as shown by necropsy. We conclude that mAb B3, when coupled to PE40 or PE, can produce strong antitumor activity in vivo. The similar level of reactivity of the B3 antibody in our tumor models with a surgical specimen of a human colon carcinoma and the toxicity study in monkeys indicate that therapeutic doses of B3-PE and B3-LysPE40 can be delivered without causing toxicity to normal organs that express B3 antigen. Although both B3-PE and B3-LysPE40 have antitumor activity in nude mice bearing a human xenograft, B3-LysPE40 is better tolerated and should be further evaluated as a therapeutic agent for cancer patients.

ADP Ribose Transferases↗

PubMed1992

EGF-R antisense RNA blocks expression of the epidermal growth factor receptor and suppresses the transforming phenotype of a human carcinoma cell line.

We have used an antisense approach to investigate the role of overexpression of the normal human epidermal growth factor (EGF) receptor in the transformed phenotype of KB cells, which are a tumor derived human cell line. Initial experiments performed in vitro, showed that antisense RNA complementary to the entire coding region (AS-FL) or to parts of the EGF-R mRNA (AS-3', AS-5', and AS-K) effectively blocked translation of EGF-R mRNA. In addition, upon microinjection into KB cells, the in vitro synthesized antisense RNAs were able to inhibit transiently the synthesis of EGF-R. Inhibition was concentration-dependent, both in vitro and in cells, and the most effective constructs were those complementary to the entire coding region (AS-FL) or to the 3'-coding end of the mRNA (AS-3'). Transfection of the same EGF-R antisense RNA constructs into the human epidermoid carcinoma KB cell line gave rise to several clones stably expressing elevated levels of antisense RNA and resulting in low residual levels of EGF receptor. The most reduced clones exhibited a totally restored serum-dependent growth and were severely impaired in colony formation and growth in agar. In addition the severity of the phenotype was directly proportional to the residual amount of EGF-R expressed. We conclude that over-expression of normal EGF-R plays a direct primary role in the development of the transformed phenotype of this human cancer cell line.

Carcinoma, Squamous Cell↗

PubMed1992

Isolation and characterization of a monoclonal antibody, K1, reactive with ovarian cancers and normal mesothelium.

We have isolated a new monoclonal antibody (MAb), K1, that reacts with an epitope on the surface of human ovarian carcinoma cells. This antibody was generated by immunization of mice with periodate-treated human ovarian carcinoma (OVCAR-3) cells. These mice had been previously made tolerant with normal human kidney membranes. Spleen lymphocytes from these mice were selected prior to fusion using a panning purification method on living OVCAR-3 cells. Initial screening of surface-reactive clones was performed in a single day using immunofluorescence on living OVCAR-3 cells, and secondary screening was performed using immunoperoxidase histochemistry on cryostat sections of normal human tissues and human tumors. The K1 clone was subcloned and identified as an IgM isotype, but was subsequently isotype-switched to IgG1K using a panning selection method. When evaluated by immunohistochemistry, the antigen reactive with K1 was found in many ovarian non-mucinous tumors, as well as in squamous tumors of the esophagus, and cervical cancer. The only normal adult human tissues showing uniform reactivity with K1 were the mesothelia of the peritoneal, pleural and pericardial cavities. There was also limited reactivity with epithelia of the trachea, tonsil and Fallopian tube. A similar tissue reactivity for K1 was found in tissues from cynomolgus monkeys. K1 reacted with many of the same tissues and tumors as the previously identified antibody OC125, but several lines of evidence indicate that K1 reacts with a different epitope and probably a different molecule, when compared to OC125. This evidence included assays employing immunofluorescence competition, double-label immunofluorescence, and solid-phase and live-cell radioimmunoassays. Since our data indicate that the antigen reactive with the K1 antibody is a new molecular species, we have named the antigen CAK1. Unlike the shed antigen CA125, CAK1 was only cell-associated and was not found in the supernatant of cultured OVCAR-3 cells or in the blood of ovarian cancer patients. The K1 antibody may be useful as a targeting agent for therapy and in the diagnosis of ovarian carcinoma, as well as some other human cancers.

Antibodies, Monoclonal↗

PubMed1992

Characterization of the antigen (CAK1) recognized by monoclonal antibody K1 present on ovarian cancers and normal mesothelium.

K1 is a monoclonal antibody that reacts with a cell surface antigen (CAK1) found in human mesothelia and nonmucinous ovarian tumors. In this article, the characteristics of the CAK1 antigen have been examined in detail. Using immunofluorescence microscopy, we have found that the CAK1 signal is removed from the cell surface by treatment with proteases or by phosphatidylinositol-phospholipase C, but not by neuraminidase and beta-galactosidase. The phosphatidylinositol-phospholipase C-released material was found to contain the CAK1 antigen which was detected by a competition radioimmunoassay. The phosphatidylinositol-phospholipase C-released CAK1 antigen was examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoblotting and found to be approximately 40 kDa protein. The CAK1-K1 antibody complex remains on the cell surface and is poorly internalized, as shown by an acid wash immunofluorescence internalization assay. An immunotoxin composed of K1 and Lys-PE40, a mutant form of Pseudomonas exotoxin lacking the cell binding domain, was not cytotoxic, supporting the conclusion that the CAK1-K1 antibody complex is not internalized. However, an immunotoxin composed of K1 and native Pseudomonas exotoxin was selectively cytotoxic to cells expressing the CAK1 antigen. This cytotoxicity is due to the fact that domain I of Pseudomonas exotoxin promotes internalization of antigens which are not internalized or bound to antibody alone. Our results suggest that CAK1 is a polypeptide that is expressed on mesothelial cells and many ovarian cancers, and that K1 may be useful as a targeting agent for the immunotherapy of human ovarian cancer.

Antibodies, Monoclonal↗

PubMed1992

Monoclonal antibody K1 reacts with epithelial mesothelioma but not with lung adenocarcinoma.

Immunoperoxidase histochemical staining of cryostat sections from human tumor tissues revealed that a murine monoclonal antibody (MAb), K1, can distinguish epithelial mesotheliomas from lung adenocarcinomas. All of 15 epithelial-type mesotheliomas and all four mixed type mesothelioma samples, but none of 23 lung adenocarcinomas with different degrees of histologic differentiation demonstrated reactivity with antibody K1. Of the cell populations in each mesothelioma tested, 80% to 100% showed strong and homogeneous staining with MAb K1. Immunofluorescence analysis of live cultured cells from an epithelioid mesothelioma (H-meso) and several lung carcinoma cell lines as well as a pleural effusion of a patient with mesothelioma also showed selective reactivity of K1 with the mesothelioma cells. These data indicate that K1 can be useful as a mesothelial cell marker for the differential pathological diagnosis of the epithelial form of mesothelioma; K1 may also be useful in the study of the pathogenesis, immunodiagnosis, and immunotherapy of epithelial-type and mixed-type human malignant mesothelioma.

Adenocarcinoma↗

PubMed1992

Monoclonal antibody C242-Pseudomonas exotoxin A. A specific and potent immunotoxin with antitumor activity on a human colon cancer xenograft in nude mice.

Two immunotoxins were constructed by chemically coupling the monoclonal antibody C242 to Pseudomonas exotoxin A (PE) or a modified form, NlysPE40, that lacks the cell binding domain of PE. Monoclonal antibody C242 recognizes a specific sialylated carbohydrate epitope on a high molecular weight membrane glycoprotein present on cells of human colon, pancreatic, and cervical cancers. C242-PE and C242-NlysPE40 were very cytotoxic for cells expressing this antigen with 50% inhibition of protein synthesis occurring on Colo205 cells at 0.2 ng/ml (0.9 pM) for C242-PE and 6.0 ng/ml (31 pM) for C242-NlysPE40. The two immunotoxins also exhibited a strong antitumor effect on a human colon cancer xenograft grown in nude mice. The specificity and potency of these two C242 immunotoxins warrant their further development for the treatment of cancer.

ADP Ribose Transferases↗

PubMed1991

In vivo regulation of monomer-tetramer conversion of pyruvate kinase subtype M2 by glucose is mediated via fructose 1,6-bisphosphate.

The activity of pyruvate kinase, subtype M2 (PKM2), is known to be increased by fructose 1,6-bisphosphate (Fru-1,6-P2), one of the metabolites in the glycolytic pathway. Recently, we have shown that in vitro, Fru-1,6-P2 activated the association of monomer to form the tetrameric PKM2. To ascertain whether this mode of regulation also occurs in vivo, we prepared monomer-specific monoclonal antibody and quantified the monomer formation in situ in cultured cells by immunocytochemistry. The intracellular Fru-1,6-P2 was manipulated by the glucose concentration in the media. At the physiological concentration of glucose (4-6 mM), 30-35% of PK existed as a monomer. However, PKM2 was dissociated into monomer within minutes after cells were deprived of glucose. The maximal level of monomer was detected after 1 h at 37 degrees C. Monomer was rapidly (within minutes) converted to tetramer after addition of glucose. Furthermore, when cells cultured in 10 mM of glucose were treated with cytochalasin B, an inhibitor of the glucose transporter, a maximal level of monomer was detected within 20-30 min. Determination of Fru-1,6-P2 indicated that its intracellular concentration decreased concomitantly with the reduction in glucose concentration in the medium. These results indicate that monomer-tetramer inter-conversion is a major in vivo cellular regulatory mechanism in response to changes in the extracellular glucose concentration via Fru-1,6-P2.

Animals↗

PubMed1991

Characterization of monoclonal antibodies B1 and B3 that react with mucinous adenocarcinomas.

B1 and B3 are two newly isolated monoclonal antibodies that react uniformly with the surface of many mucinous carcinomas of the colon, stomach, and ovary but with a limited number of normal tissues, among which are glands of the stomach, epithelia of the trachea and bladder, differentiated epithelium of the esophagus, and small bowel mucin. They also react uniformly with many human tumor cell lines, including MCF7, MDA-MB-468, and HTB20 (breast), A431 (epidermoid), HT29 (colon), HTB33 (cervical), and DU145 (prostate). Immunoprecipitation experiments indicate that B1 and B3 react with epitopes present on a large number of glycoproteins, ranging in molecular weight from greater than 200,000 to less than 40,000. Using a panel of 37 different carbohydrate residues attached to albumin to form neoglycoproteins, it was found that B1 reacts with Ley and H-type 2 and B3 reacts with Ley, di-Lex, and tri-Lex antigens. Thus, each antibody reacts with a distinct portion of a carbohydrate residue. Because of the limited reactivity of these antibodies with normal tissues, they merit evaluation in the treatment of cancer.

Adenocarcinoma, Mucinous↗

PubMed1991

Magnetic-affinity cell sorting of human multidrug-resistant cells.

We have developed a method for isolating multidrug-resistant cells from a heterogeneous cell population using the magnetic-affinity cell-sorting system. Human KB carcinoma cell lines expressing different amounts of P-glycoprotein have been selected by use of the monoclonal antibody MRK-16 coupled to magnetic particles. This specific, rapid, and sensitive method allows the selection of viable and clonable drug-resistant cells from various drug-resistant human and murine cell populations. This method may prove useful in isolating drug-resistant cells from tumors with heterogeneous P-glycoprotein expression for further analysis.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1991

Anti-tumor activities of immunotoxins made of monoclonal antibody B3 and various forms of Pseudomonas exotoxin.

B3 is a monoclonal antibody that reacts with a carbohydrate epitope present on a variety of proteins located on the surface of many cancer cells and a limited number of normal tissues. We evaluated the cytotoxic activity of immunotoxins composed of monoclonal antibody B3 coupled to native Pseudomonas exotoxin (PE) or two recombinant forms of Pseudomonas exotoxin, PEArg57 or LysPE40, a form of PE with a deletion of the cell binding domain. All three conjugates were cytotoxic to human cell lines expressing the B3 antigen on their surface. The survival of each of the three immunotoxins in the circulation of mice was determined after administering the immunotoxin i.v. The half-life in blood of B3-PE and B3-PEArg57 was 20 hr, whereas the half-life of B3-LysPE40 was 4 hr. The short half-life of B3-LysPE40 may be due to the absence of domain I of PE. To determine the therapeutic effects of the three immunotoxins, they were given intraperitoneally to nude mice bearing subcutaneous A431 tumors. All three immunotoxins caused complete regression of 50-mm3 tumors with no toxic effects to the animals at therapeutic doses. Furthermore, substantial regression was also noted with much larger tumors. Our data indicate that the monoclonal antibody B3, when coupled to PE or recombinant forms of PE, may be useful for the treatment of tumors expressing B3 antigen. The therapeutic window was largest with B3-LysPE40, which can be administered in higher doses because it lacks sequences in domain I of PE that enable PE to bind to nontarget cells.

ADP Ribose Transferases↗

PubMed1991

Characterization by somatic cell genetics of a monoclonal antibody to the MDR1 gene product (P-glycoprotein): determination of P-glycoprotein expression in multi-drug-resistant KB and CEM cell variants.

We isolated an IgG2a murine monoclonal antibody (MAb) termed MAb57, specifically reactive with multi-drug-resistant (MDR) human cells. Its specificity toward the MDRI gene product (P-glycoprotein) has been demonstrated by the concordant segregation of the MAb57 epitope with the MDRI gene in interspecific mouse x human cell hybrids, and the reactivity of several different MDRI gene-expressing cells with MAb57, particularly insect cells acutely infected with a baculovirus encoding the MDRI gene. MAb57 can be used to detect, by flow cytometry, variations in the relative drug-resistance levels of several MDR KB and CEM cell variants. This immunological probe has also proven useful in selectively destroying MDR target cells in an antibody-dependent cell-mediated (ADCC) assay system as well as in detecting P-glycoprotein expression in normal and malignant tissues and cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1991

Molecular manipulations of the multidrug transporter: a new role for transgenic mice.

Multidrug resistance in human cancer is associated with overexpression of the MDR1 gene which encodes a 170,000 molecular weight membrane glycoprotein that transports cytotoxic drugs out of cancer cells. The MDR1 gene is normally expressed in intestine, kidney, liver, and adrenal glands, and in tumors derived from these tissues, but it is not expressed in normal bone marrow. Transgenic mice that express the MDR1 gene in their bone marrow have been developed, and because of this expression these mice are resistant to the bone marrow-suppressive effects of daunomycin, doxorubicin, taxol, and several other anticancer drugs. These mice can be used in several different ways to develop new types of drugs to treat human cancer.--Pastan, I.; Willingham, M. C.; Gottesman, M. Molecular manipulations of the multidrug transporter: a new role for transgenic mice.

Animals↗

PubMed1991

Inactivation of a sperm motility gene by insertion of an epidermal growth factor receptor transgene whose product is overexpressed and compartmentalized during spermatogenesis.

Transgenic mice were generated with a human epidermal growth factor (EGF) receptor cDNA driven by the chicken beta-actin gene promoter. One line (AE24) that exhibited a unique expression pattern in which dramatically elevated levels of EGF receptor RNA were found only in the testis was established, suggesting that the beta-actin promoter was being influenced by an adjacent testis-specific enhancer. EGF receptor RNA was detected in primary spermatocytes, whereas the synthesis of receptor protein was restricted to elongate spermatids, indicating that transgene expression was under translational control. At spermiation, the EGF receptor was sequestered in residual bodies and excluded from mature sperm by a compartmentalization mechanism. About half of AE24 homozygous males were sterile because of sperm paralysis, whereas heterozygous males and females of either genotype were completely fertile. Electron microscopic analysis of sperm flagella from sterile AE24 homozygotes revealed an aberrant axonemal structure in which outer doublet microtubules were missing from the middle piece, resembling changes observed in the sperm of some infertile humans. Flagellar axonemal disassembly was observed in the vas deferens and epididymis but not in the testis, suggesting that outer doublets were assembled in a grossly normal manner but possessed a latent instability. These results demonstrate that in the AE24 mouse line the EGF receptor transgene was integrated into and inactivated an endogenous autosomal gene, causing sperm flagellar axonemal disruption and male sterility.

Actins↗